Numerous polymer-based medical devices have been developed for implantation or insertion into the body. For example, in recent years, drug eluting coronary stents, which are commercially available from Boston Scientific Corp. (TAXUS), Johnson & Johnson (CYPHER) and others, have become the standard of care for maintaining vessel patency. These existing products are based on metallic balloon expandable stents with biostable polymer coatings, which release antiproliferative drugs at a controlled rate and total dose.
Specific examples of biostable polymers for drug eluting polymer coatings include block copolymers of polyisobutylene and polystyrene, for example, polystyrene-polyisobutylene-polystyrene triblock copolymers (SIBS copolymers), which are described in U.S. Pat. No. 6,545,097 to Pinchuk et al., which have proven valuable in implantable and insertable medical devices for a variety of reasons, including their excellent elasticity, strength and biocompatibility. SIBS copolymer systems are also effective drug delivery systems for providing therapeutic agents to sites in vivo.
Biodegradable polymers, on the other hand, offer the potential of reducing or eliminating long term effects that may be associated with non-biodegradable polymers (e.g., foreign body effects, etc.), because they are metabolized over time.